Stevens T. Mason, age 19, became Governor of the Michigan Territory in 1835. Mason inherited the post when both the incumbent – Lewis Cass, and the territorial secretary, Mason’s father, left the territory. 160 citizens protested the appointment by President Andrew Jackson of someone so young, so Jackson fired Mason and appointed John Horner instead. But Horner promptly died of cholera. Again Mason was put in charge, and he called for a census, a constitutional convention, and election of state officials. Further, he took command of the territorial militia and occupied disputed territories.
In the ensuing elections, Michiganders approved the constitution overwhelmingly, and elected Mason to be their governor. [Both the terms “Michigander” and “Michiganian” are considered correct, according to the Michigan state government. In any event, neither one could be said to be accurate, since the name Michigan is derived from the Ojibwa (Chippewa) word “meicigama” (phonetically Michi-gama) for “big water.” But Michigan sounds better than Michigam.]
In June, 1836, Congress offered statehood to Michigan on the condition that it cede Toledo to Ohio and take the Upper Peninsula in exchange. Mason, aware that President Jackson was about to distribute parts of the federal surplus to states, felt it was a fine time to join, and Michigan accepted the deal, joining the Union on this day in history.
According to a Michigan state university site, some of the names of the counties in Michigan have themes:
You can see the derivation of the rest of the county names here.